Endoscopy (EGD, EUS, ERCP)

A colonoscopy probably does reduce bowel cancer risk for the person who has it, but a programme that offers colonoscopy achieves much less if most people decline. Programmes based on stool tests with high uptake may deliver as much population benefit at lower cost and risk.

Durability is what makes endoscopic screening cost-effective: one procedure at 55 buys nearly two decades of protection, which is the argument for long intervals rather than frequent tests.

The clinical proof of Vogelstein's sequence: interrupting the adenoma-carcinoma pathway with a snare prevents the cancer, which is why colonoscopy is the only screening test that both detects and prevents.

The trial behind England's short-lived bowel scope screening programme, and the clearest demonstration that one endoscopic look, by removing adenomas, prevents cancer rather than only advancing its diagnosis.

The paper that made the adenoma detection rate the central quality measure of every screening endoscopy service, and the reason endoscopist-level auditing is a condition of accreditation.

The evidence that a cheap home test posted to a whole population saves lives, and the reason England, Scotland, Wales and Northern Ireland all run bowel screening programmes; the 40 percent who never did the test are the reason uptake is still the biggest lever.